This glycopeptide is a 16-amino acid modified fragment of mucin 5/MUC5AC, where T* is a GalNac labeled threonine 3. Mucin-type linkages (GalNAc 1-O-Ser/Thr) are initiated by a family of glycosyltransferases known as the UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferases (ppGaNTases). These enzymes transfer GalNAc from the sugar donor UDP-GalNAc to serine and threonine residues, forming an alpha anomeric linkage. The MUC5AC gene, which is mainly expressed in gastric and respiratory mucosae, exhibits 8 amino acid tandemly repeated domain, the consensus peptide TTSTTSAP.